AIIM Research - Enterprise 2.0: Agile, Emergent & Integrated (available at AIIM.org) concludes the following:
RSS is a family of Web feed formats used to syndicate content to other sites. An RSS channel or feed provides either a summary of targeted Web content or the full text. RSS dynamically and automatically keeps subscribers aware of content changes (additions and edits) to targeted Websites (e.g., a Blogs or Wikis).
RSS content is read using software known as a reader, or aggregator. Users subscribe to a feed by entering the feeds link into the reader or by clicking an RSS icon in a browser initiating the subscription process. The reader checks the user's subscribed feeds regularly for new content, downloading any updates it finds.
RSS is the most popular form of signal functionality in Enterprise 2.0. It is standards-based, and formatted as XML for easy consumption and transformation by feed readers, aggregators, dashboards, or mashups. RSS (and ATOM, another type of feed) are pull-based, rather than push-based communication streams, such as e-mail.
RSS feeds can be used to provide emergence by monitoring the popularity of subscriptions (i.e. most popular sites). They can also be "nested," meaning an RSS feed can serve as a trigger to another signal.
For a great introduction to RSS use, see RSS in Plain English on YouTube.